The proposed experiments investigate choice behavior. One group of experiments assesses the PI's delay-reduction hypothesis of choice and conditioned reinforcement which states that the effectiveness of a stimulus as a conditioned reinforcer may be predicted most accurately by calculating the reduction in the length of time of primary reinforcement correlated with the onset of the stimulus in question relative to the length of time to primary reinforcement measured from the onset of the trail. In other words, the greater the improvement, in terms of temporal proximity or waiting time to reinforcement, correlated with the onset of a stimulus, the more effective that stimulus will be as conditioned reinforcer. The proposed experiments use the concurrent-chains procedure to assess (1) the relative contribution of the delay-reduction and primary reinforcement rate factors that make the delay-reduction equation; (2) the primary hypotheses that frequency of conditioned reinforcement has no direct effect on choice in this procedure; (3) conditions in which delay-reduction predicts sharply nonoptimal choice. The second proposed set of studies also involves the sensitivity of choice to reinforcement variables, however these studies are especially relevant to models of foraging in behavioral ecology, to self-control and to species and reinforcer differences that may affect sensitivity to relatively short-term versus relatively long-term reinforcement opportunities. A third set of studies follows up our assessment of choice as a function of economic context including assessment of: (1) the generality of the bitonic function relating responding to reinforcement; (2) the effects of economic context on choice and conditioned reinforcement in chain schedules; (3) the relation of risk-aversion and risk-proneness to economic context. Other studies assess the conditions under which information, especially about physical health, reinforces human behavior. Topics such as self-control, conditioned reinforcement, choice-including nonoptimal decision-making - and the reinforcing status of information all have relevance for health concerns.